This invention relates generally to ignition systems for internal combustion engines. More particularly, this invention relates to laser ignition systems and features that optimize a laser ignition system for internal combustion engines.
For internal combustion engines, fuel is combusted with an oxidizer (usually air) in combustion chambers. The resulting high temperature and pressure gases expand and thereby apply forces to movable components of the engines, such as turbine blades to drive the turbine. Combustion can be intermittent (as for example, in automotive applications) or continuous (as for example, in gas turbines and jet engines).
In a conventional ignition apparatus for internal combustion engines, a high voltage is applied to an ignition plug that is fixed on a wall surface of the combustion chamber in order to ignite an air-fuel mixture by spark discharge. However, in an ignition apparatus of this kind, since the ignition plug is exposed directly to the combustion chamber, carbon attaches to the ignition plug to render the discharge of the ignition plug difficult. Furthermore, due to a heat loss of the electrodes of the ignition plug, a torch or nucleus of flame generated by the discharge is cooled, and vanishes before reaching a flame. Additionally, since the ignition occurs on or very near the wall surface, poor mixing often results due to the difficulties associated with burning fuel from the wall surface.
Engines that use combustible fuel such as, for example, gas turbine engines and other internal combustion engines include combustion areas such as, for example, combustors or cylinder and piston assemblies that facilitate the conversion of energy from combustion into mechanical energy. Fuel nozzles are used to introduce atomized fuel into the combustion areas. The atomized fuel is ignited by an igniter. Igniters may include, for example, electrical igniters that create a spark proximate to the atomized fuel, heating elements that introduce heat to the atomized fuel, and igniters that introduce a flame in the combustion area. In an attempt to enhance mixing and flame stabilization, optimizing this laser assisted atomization and pre-ionization by the laser light is desired.
In addition, in conventional diagnostics system for internal combustion engines, optical measurements of flame chemiluminescent light emissions are routinely used in premixed gas combustors to determine various parameters such as energy or heat release rates and fuel-to-air ratios in such combustors. Placing wavelength filters in front of optical detectors is typically used to identify the partial contribution of the total light emission from each of specific excited-state species. Ratios of the signals of one or more of these species can then be correlated in a known manner to various combustor parameters such as the fuel-to-air ratio, heat release rate and gas temperature. Previous applications of this measurement technique have used simple optical sensor arrangements and camera systems.
Typically, the ignition apparatus and the diagnostics apparatus are formed as separate systems that utilize separate and discrete components within a combustion engine. However, results can be improved by providing for optimized ignition configurations and diagnostics using optical techniques in each combustor can.
Therefore, there is a need for a new and improved optimized ignition system and method for internal combustion engines in which an optimized laser ignition is provided in an attempt to enhance mixing and flame stabilization in combination with an integrated diagnostics apparatus.